A speed change control device in an automatic transmission is composed for example of a microcomputer etc. and a correlation between an accelerator opening and vehicle speed by which a shifting of each speed stage is commenced in each range is stored as a shift map in a storage means composed of a memory etc. In a shift map of a conventional speed change control device, a shift point has moved toward a high speed side with an increase in an accelerator opening as shown by FIG. 5. Consequently, as indicated by arrows A and B in FIG. 5, an automatic transmission has carried out a shift-up operation when an accelerator pedal has been released during running under a state of a large accelerator opening, and the automatic transmission has carried out a shift-down operation when the accelerator pedal has been fully trod down from the foregoing state. In FIG. 5, an axis of abscissa denotes the vehicle speed and an axis of ordinate denotes the accelerator opening, a solid line C denotes a shift-up timing from 1st speed to 2nd speed, a solid line D denotes a shift-up timing from 2nd speed to 3rd speed, a broken line E denotes a shift-down timing from 2nd speed to 1st speed, and a broken line F denotes a shift-down timing from 3rd speed to 2nd speed, respectively.
A vehicle, such as a commercial car powered by a small engine torque relatively to its weight, has frequently subjected to a driving condition with an accelerator pedal opened to a large extent in a driving along a mountain road or in a driving with a heavy weight loaded, so that a vehicle equipped with a conventional speed change control device frequently encounters a so-called hunting state wherein shift-up and shift-down occur very often to cause a bad drive feeling in a driving along a mountain path such as a meandering road on which the accelerator pedal has to be opened and closed frequently. Further, when driving a road with frequent uphill and downhill, an engine braking effect has become worse due to the shift-up so that a driver has been forced to operate frequent braking actions.